Every former head of the DEA since it was created by Richard Nixon in 1973 has signed onto a letter to Attorney General Eric Holder urging him to speak out against the marijuana legalization initiatives on the ballot in three Western states. The former top narcs warned that silence would be seen as acquiescence.

"We urge you to oppose publicly Amendment 64 in Colorado, Initiative 502 in Washington, and Measure 80 in Oregon," the former DEA chiefs wrote. "To continue to remain silent conveys to the American public and the global community a tacit acceptance of these dangerous initiatives."

Legalization at the state level would be a "direct violation of the Controlled Substance Act," they wrote. "Since these initiatives would 'tax and regulate' marijuana, there is a clear and direct conflict with federal law."

The former top narcs said they were "encouraged" by Holder's having spoken out against California's 2010 Proposition 19 and by President Obama's strong stance against legalization. They urged Holder to take a public position against the initiatives "as soon as possible."

Reuters reported that Holder's office had no comment on the letter, but former ONDCP official Kevin Sabet told the news agency he wouldn't be surprised if Holder again spoke out against legalization.

"Essentially, a state vote in favor of legalization is a moot point since federal laws would be, in (Holder's) own words (from 2010), 'vigorously enforced,'" Sabet said. "I can't imagine a scenario where the Feds would sit back and do nothing."

But marijuana legalization backers described themselves as unsurprised by the letter and were quick to strike back.

"Anyone who is objective at all knows that current marijuana policy in this country is a complete disaster, with massive arrests, wasted resources, and violence in the US and especially in Mexico," said Jill Harris, managing director of strategic initiatives for Drug Policy Action, the lobbying arm of the Drug Policy Alliance.

"It is not surprising that these men, who have made a living off of marijuana prohibition, want their successors to continue profiting from the existence of the underground marijuana market," Tvert wrote. "They just want to keep billions of taxpayer dollars flowing to their buddies. They know that marijuana prohibition isn't really improving public safety; just as our nation's streets weren't safer when Al Capone and his cohorts controlled the alcohol trade," he added.

"For Eric Holder to act as the mouthpiece for these old school warriors of the irrational war on marijuana that is rapidly losing public support would be sending a message to tens of thousands of passionate supporters of Amendment 64 that their opinions do not matter," Tvert warned the administration. "He will be telling them that Colorado must continue to live under a system of marijuana prohibition not because it makes sense, but because the federal government demands it. Most people accept the view that drug prohibition has been a colossal failure."